Travel documentation question...

My family moved to Brussels 4 months ago from the U.S. We have registered with the commune and completed the police visit, but have not yet received our ID cards. We are planning to return to the U.S. for the Christmas holiday, and I'm wondering if we will have any problems leaving, or returning to Belgium, given that our 3-month tourist visas have expired. I know that we should technically we should not travel, but does anyone have any experience with this? I've read mixed reviews about whether a U.S. passport + Belgian work permit + Belgian "modele 2" document would be sufficient for re-entry...

Any thoughts on how risky this might be?

thanks